I've had them on my 1946 235 for over a year. Have them between the head and manifolds and cut my own to fit between the two manifolds using one of their blank square pieces, as I didn't see them having a pre-cut one for my application. So far there are 0 leaks and the material looks identical to the way it did when it was installed, excepting there is some separation at the first and last studs, but it happened on the initial heat cycle and hasn't changed since or leaked at all. Definitely an upgrade over the other material. Although my head and manifolds are pretty flat, it seems the other material would eventually rust and would work itself into a leak at one of the exhaust ports after about 2 years or so, and usually on a different port each time. There isn't anything to rust in this stuff so it should last for a while. I believe there are some photos in my gallery of the install.
